KR20120062333A - Electrode of secondary cell including por0us insulating layer and manufacturing thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of a secondary battery electrode including a porous insulating layer and an electrode manufactured with the manufacturing method are provided to simplify formation process of the porous insulating layer and to obtain strong structural stability. CONSTITUTION: A manufacturing method of a secondary battery electrode including a porous insulating layer comprises the following steps: coating electrode layer slurry on surface of an electrode(100); spreading the porous insulating layer before the electrode layer is dried; and desiccating the electrode layer slurry and the porous insulating layer coated slurry at the same time. The porous insulating layer is independently coated with inorganic compound powder or with a compound powder of the functional inorganic compound additive and inorganic compound powder.

Description

Secondary battery electrode comprising a porous insulating layer and a method of manufacturing the same {ELECTRODE OF SECONDARY CELL INCLUDING POR0US INSULATING LAYER AND MANUFACTURING THEREOF}

The present invention relates to a method for manufacturing an electrode for use in a secondary battery and a secondary battery produced by the same, and more particularly, to introduce a porous insulating layer (porous insulating layer) made of an inorganic compound or the like on the surface of the electrode, The present invention relates to a technique of coating a porous insulating layer slurry in an undried state and then simultaneously drying the electrode slurry so that the binder does not shield the porous structure of the electrode layer.

In general, a secondary cell is a chemical cell capable of repeating charging and discharging by using a reversible interconversion of chemical energy and electrical energy, and is a positive electrode, a negative electrode, a separator, and an electrolyte. It has four basic components called electrolytes.

The positive electrode and the negative electrode are electrodes that actually convert and store energy such as oxidation / reduction, and have relatively positive and negative potentials, respectively. The separator is positioned between the anode and the cathode to maintain electrical insulation and provides a path for charge transfer, and the electrolyte serves as a medium for charge transfer.

The electrode material is a material that actually reacts among the electrode constituent materials, and is also called an active material.

Most of the anode material is a material capable of intercalation of lithium ions, and the cathode material is often a lithium metal, an alloy, or a compound capable of intercalation of lithium ions.

The separator is in the form of a porous polymer membrane or a nonwoven fabric, and has a structure of a single layer or a multi layer membrane. The introduction of a liquid electrolyte composed of an organic solvent and a salt may provide a movement path for ions moving between the positive electrode and the negative electrode during the charge and discharge of the battery.

The organic solvent is preferred to have high polarity and no reactivity with lithium metal in order to increase dissociation of ions by increasing the polarity of the electrolyte and to facilitate conduction of ions by lowering the local viscosity around the ions.

Hereinafter, a manufacturing process of a conventional electrode will be described.

The manufacturing process of the electrode is generally carried out in five stages: material weighing, mixing, coating, drying, and pressing.

Material metering is a step of measuring the electrode constituent material including the electrode material according to a predetermined composition ratio, mixing is a step of dissolving, dispersing and kneading by introducing the electrode constituent material in a certain order. In general, after the mixing process is completed in the form of a slurry (slurry) is to be added to the coating process. That is, the mixed slurry is composed of an electrode constituent material and a dispersion medium, and the electrode constituent material is composed of the above electrode material (active material), a conductive material, a binder, and other additives. As shown in FIG. 1, the coating and drying process is performed by unwinding the electrode from the unwinder 10 and applying it through the coating chamber 20, and then moving to the drying furnace 30 to rewind the rewinder 40. I will perform as I build.

The mixing process is a process of dissolving, dispersing, and kneading the electrode constituent material, which includes dry mixing the powdered electrode constituent material, that is, the electrode material, the conductive material, the polymer binder, and the like in a closed container, and then using the solvent of the polymer binder, or Dissolve and disperse in the dispersion medium.

The coating and drying process is a step of coating the slurry obtained by mixing the above materials on an electrode current collector and drying to obtain an electrode composed of only solid content.

The current collector is a material that collects electrons obtained from the oxidation / reduction reaction of the electrode material and flows to an external conductor.

The rolling process is a process of applying the electrode in a completely dry or semi-dry state obtained through a coating and drying process under a certain thickness and pressure.

As described above, the material is finally weighed, mixed, applied, dried, and rolled into a final electrode.

Secondary batteries manufactured by the above process, in particular lithium secondary batteries have a problem with regard to safety in that they have a high energy density and use a combustible material such as an organic solvent.

The main cause of safety-related accidents in batteries is the arrival of abnormal high temperatures due to short circuits between the positive and negative electrodes. That is, under normal circumstances, the separator is positioned between the positive electrode and the negative electrode to maintain electrical insulation, but the battery may cause overcharge or overdischarge, or may cause internal short circuit due to dendritic growth or foreign matter of the electrode material. In an abnormal misuse situation such as a sharp object such as a screw penetrating a battery or an excessive force applied to the battery by an external force, the existing separator may show a limit.

The separator is mainly a microporous membrane made of a polyolefin resin, but its heat resistance temperature is about 120 ~ 160 ℃ is insufficient heat resistance. Therefore, when an internal short circuit occurs, there is a problem that the separator contracts due to the short-circuit reaction heat, causing the short-circuit to be enlarged and to a thermal runaway state in which a larger amount of reaction heat is generated.

The present invention has been made to solve the above problems, the porous insulating layer in an undried state after applying the electrode layer slurry to form a porous insulating layer consisting of inorganic compound powder and a polymer binder on at least one surface of the positive electrode and the negative electrode An object of the present invention is to provide a method of manufacturing an electrode for a secondary battery, which can simplify the process by coating a slurry or an inorganic compound powder and simultaneously drying the same, and solve the battery stability problem.

Embodiments of the present invention for achieving the above object, the electrode manufacturing method for forming a porous insulating layer on at least one electrode surface of the cathode or the anode, comprising: applying an electrode layer slurry on the electrode surface; Applying a porous insulating layer in an undried state of the electrode layer slurry; Simultaneously drying the electrode layer slurry and the porous insulation layer coating slurry; It provides a secondary battery electrode manufacturing method comprising a porous insulating layer comprising a.

The porous insulating layer of the embodiment according to the present invention may be applied by the inorganic compound powder alone or by a mixed powder of the inorganic compound powder and the functional inorganic compound additive.

The porous insulating layer of the embodiment according to the present invention is applied by a porous insulating layer coating slurry containing a polymer binder, the solvent of the polymer binder and the solvent of the polymer binder of the electrode layer slurry is volatile and may be a good solvent.

 The porous insulating layer of the embodiment according to the present invention is applied by a porous insulating layer coating slurry containing a polymer binder, the solvent of the polymer binder and the solvent of the polymer binder of the electrode layer slurry is volatile, may be a poor solvent or a non-solvent.

The electrode of the embodiment according to the present invention may include an active material, a conductive material, a polymer binder, an additive.

When the electrode of the embodiment according to the present invention is a negative electrode, the active material is at least one of a graphite or carbon-based material, when the electrode is a positive electrode, the active material is a transition metal-oxide, transition metal-phosphate-based, transition metal-silicate It is characterized in that at least one of the type, transition metal-sulfate-based or polymer material.

The conductive material of the embodiment according to the present invention is characterized in that at least one selected from graphite, carbon black, activated carbon, carbon nanotubes and carbon nanofibers.

The polymer binder of the embodiment according to the present invention is a polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and maleic anhydride, polyvinyl chloride, polyvinyl alcohol, poly Vinyl formal, polymethyl methacrylate, polymethacrylate, tetraethylene glycol diacrylate, cellulose triacetate, polyurethane, polysulfone, polyether, polyolefin, polyethylene oxide, polyisobutylene, polybutyldiene, poly At least one selected from acrylonitrile, polyimide, acrylonitrile-butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene monomer, polydimethylsiloxane, and silicone polymer.

The solvent of the polymer binder of the embodiment according to the present invention is N-methylpyrrolidinone, dimethylformamide, dimethylacetamide, hexamethylphosphoamide, acetonitrile, acetone, cyclohexanone, dimethyl sulfoxide, tetrahydrofuran, di It is characterized in that at least one selected from oxene, chloroform, dichloromethane, water.

The poor or good solvent of the embodiment according to the present invention is N-methylpyrrolidinone, water, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, glycerol, acetone, dimethyl ether, diethyl ether, ethyl acetate, dichloro It is characterized in that at least one selected from methane.

Inorganic compound powder of an embodiment according to the present invention is characterized in that at least one selected from SiO ₂ , Al ₂ O ₃ , TiO ₂ , SnO ₂ , ZnO, CeO ₂ , ZrO ₂ , BaTiO ₃ , Y ₂ O ₃ .

Inorganic compound powder of an embodiment according to the invention is characterized in that the size of 0.001 ~ 1 ㎛.

The content of the inorganic compound powder of the embodiment according to the present invention is characterized in that at least 10% by weight of the porous insulating layer solids.

Additives of the inorganic compound, a functional embodiment of the present invention is characterized in that at least one member selected from _{AlX 3, MgX 2, SnX 2} , wherein X is a halogen element.

The additive of the functional inorganic compound of the embodiment according to the present invention is characterized in that 0.1 to 10% by weight of the porous insulating layer solids.

The coating thickness of the porous insulating layer of the embodiment according to the invention is characterized in that 1 ~ 10㎛ after drying.

Porous insulating layer of the embodiment according to the invention is characterized in that the drying at 50 ℃ ~ 200 ℃.

According to an embodiment of the present invention, in an electrode forming a porous insulating layer on at least one electrode surface of a cathode or an anode, an electrode layer slurry is coated on the electrode surface, and the surface of the electrode layer slurry is undried in the electrode layer slurry. The porous insulating layer coating slurry is applied to the electrode layer slurry and the porous insulating layer coating slurry is dried at the same time to provide a secondary battery electrode comprising a porous insulating layer that the binder of the porous insulating layer does not block the porous structure of the electrode layer.

As described above, the present invention connects the porous structures of the electrode layer and the porous insulating layer integrally, and the porous insulating layer is formed by applying the electrode layer and the porous insulating layer to a three-step process of applying and drying the electrode layer and the porous insulating layer. Not only can the formation process be simplified, but the slurry or inorganic compound powder of the porous insulating layer is applied while the solvent remains before the electrode layer is dried, and dried, thereby integrally in the process of simultaneously volatilizing the porous insulating layer and the solvent of the electrode layer. The connected porous structure is formed, and by applying the porous insulating layer in an undried state, the electrode layer polymer binder and the porous insulating layer polymer binder are more effectively bound, thereby securing a stronger structural stability of the porous insulating layer.

1 is a schematic view of a conventional electrode manufacturing process.
2 is a SEM photograph of the negative electrode according to the comparative example.
3 is a cross-sectional view of an electrode according to an embodiment of the present invention.
4 is a schematic diagram of an electrode manufacturing process including coating a porous insulating layer according to an exemplary embodiment of the present invention.
5 is a SEM photograph of the negative electrode according to the embodiment of the present invention.
Figure 6 is a graph showing the capacity maintenance and life characteristics test results according to the charge-discharge iteration of the secondary battery manufactured by Examples and Comparative Examples of the present invention.
Figure 7 is a graph showing the results of capacity expression experiment according to the discharge current applied value of the secondary battery prepared by Examples and Comparative Examples of the present invention.
Figure 8 is a graph showing the results of the overcharge stability test of the secondary battery prepared by Examples and Comparative Examples of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Such an embodiment may be embodied in various different forms as one of ordinary skill in the art to which the present invention pertains, and is not limited to the embodiments described herein.

FIG. 4 is a process diagram of applying a porous insulating layer according to an exemplary embodiment of the present invention, except that the coating chamber 50 is added, which is the same as the electrode manufacturing process illustrated in FIG. 1.

3 is a cross-sectional schematic view of a secondary battery using the negative electrode 160, in particular, according to an embodiment of the present invention, which includes a negative electrode 160, a negative electrode current collector 170, and a porous insulating layer ( 150, the separator 130, the anode 110, and the cathode current collector 120 are stacked.

First, the method of applying the porous insulating layer to the surface of the electrode layer in the embodiment of the present invention will be described.

First, a method of applying the porous insulating layer in the inorganic compound powder alone or mixed powder with functional inorganic compound additives,

Second, the polymer binder is introduced into the porous insulating layer, but both the solvent of the polymer binder of the porous insulating layer coating slurry and the solvent of the polymer binder of the electrode layer slurry are volatile, and they are good solvents of the polymer binder of the counter layer. , How you can mix with each other,

Third, a polymer binder is introduced into the porous insulating layer, wherein both the solvent of the polymer binder of the porous insulating layer coating slurry and the solvent of the polymer binder of the electrode layer slurry are volatile, and each other is a poor solvent or There is a non-solvent method that can be mixed with each other.

The production of the electrode layer to be described later is commonly applied. First, powdery electrode components, that is, electrode material, conductive material and polymer binder are dry mixed in a sealed container, and then dissolved and dispersed in a solvent of the polymer binder. The mixing process may be any method commonly used, and a magnetic stirrer, a mechanical stirrer, an oil stirrer, an ultrasonic stirrer, or the like is preferable.

The electrode material may be any material commonly used in secondary batteries, particularly lithium secondary batteries. In the case of the negative electrode material, carbonaceous materials such as graphite-based or hard or graphitizable carbon such as artificial graphite or natural graphite may be used. The system is preferred, and in the case of the positive electrode material, a transition metal-oxide type, a transition metal-phosphate type, a transition metal-silicate type, a transition metal-sulfate type, or a polymer material is preferable as described above.

The conductive material may be any material commonly used for secondary batteries, particularly lithium secondary batteries, and carbon-based materials such as graphite, carbon black, activated carbon, carbon nanotubes, and carbon nanofibers are preferable.

Almost all ordinary polymers can be used as the polymer binder, including polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, vinylidene fluoride and maleic anhydride. (maleic anhydride) copolymer, polyvinylchloride, polyvinylalcohol, polyvinyl formal, polymethylmethacrylate, polymethacrylate, tetraethylene Tetra (ethylene glycol) diacrylate, cellulose triacetate, polyurethane, polysulfone, polyether, polyolefin such as polyethylene or polypropylene, Polyethylene oxide, polyisobutylene, polybutyldiene, poly Acrylonitrile, polyimide, acrylonitrile-butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene monomer ), One or two or more mixtures or copolymers thereof selected from the group consisting of polydimethylsiloxane and polysilicone.

In addition, as a solvent of the polymer binder, N-methylpyrolidinone (N-methylpyrolidinone), dimethylformamide, dimethylacetamide, hexamethylphosphoramide, hexamethylphosphoramide, acetonitrile, acetone one or two selected from the group consisting of (acetone), cyclohexanone, dimethylsulfoxide, tetrahydrofuran, dioxane, chloroform, chloroform, dichloromethane and water The above mixture is preferable.

As the poor solvent or nonsolvent of the polymer binder, N-methylpyrrolidinone, water, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol (ethylene glycol), glycerol (glycerol), acetone, dimethyl ether (dimethylether), diethyl ether (diethylether), ethylacetate (ethylacetate) and dichloromethane selected from the group consisting of dichloromethane is preferred.

The inorganic compound powder is a ceramic particle commonly used in the art to which the present invention pertains, and is not particularly limited as long as it is stable within the operating voltage (0 to 5 V based on Li / Li +) of the battery. Since these inorganic compound powders exhibit strong mechanical properties and excellent heat resistance at high temperatures, when they are placed on the surface of the electrode layer, they are safe from heat generation, membrane shrinkage deformation due to electrical, mechanical and environmental misuse, and due to internal short circuits between the anode and the cathode. Since no degradation occurs, it exhibits a very safe characteristic.

The inorganic compound powders include SiO ₂ , Al ₂ O ₃ , TiO ₂ , SnO ₂ , ZnO, CeO ₂ , ZrO ₂ , BaTiO ₃ , Y ₂ O ₃ , and the like. Can also be used. The size of the inorganic compound powder is not limited, but in order to maintain uniform dispersion, thickness control of the coating layer, and proper porosity, it is preferably in the range of 0.001 to 1 μm.

If the size of the inorganic compound powder is less than 0.001 μm, it is difficult to prepare a slurry for the porous insulation layer or it is difficult to uniformly coat the surface of the electrode layer. Not only the size of the formed pores is too large but also the thickness of the porous insulating layer can not be properly adjusted.

In addition, the content of the inorganic compound powder is preferably 10% by weight or more, more preferably 30% by weight or more, in the porous insulating layer solids (inorganic compound + polymer binder). When the inorganic compound content is 10% by weight or less, it is difficult to expect improvement of heat resistance or mechanical properties by applying the inorganic compound.

The functional inorganic compound additives are added to form a uniform solid electrolyte interface on the electrode surface during the charge / discharge reaction of the battery to improve battery life and high rate characteristics. Such functional inorganic compounds include AlX ₃ , MgX ₂ , and SnX. ₂ (X is a halogen element) etc. are preferable.

A more detailed role of the functional inorganic compound additive is to form a protective film by reacting with lithium ions during charging and discharging, or to form a protective layer by surface adsorption of an electrode, thereby improving life characteristics of a lithium secondary battery.

The content of the functional inorganic compound is preferably in the range of 0.1 to 10% by weight of the porous insulating layer solids (inorganic compound + functional inorganic compound + polymer binder). When the content of the functional inorganic compound is less than 0.1% by weight, the solid electrolyte interface may not be sufficiently formed on the surface of the electrode, and thus, life expectancy may not be improved. When the content of the functional inorganic compound exceeds 10% by weight, the manufacturing cost increases.

After the polymer binder is completely dissolved and uniformly dispersed and mixed with the electrode constituent material, the slurry is poured onto the foil, which is an electrode current collector, and adjusted to a certain thickness to be applied in the form of a film. The application process may be generally made in the form of a film. If there is a method, generally, a comma method, a slit die method, a gravure method, a doctor blade method, a silk screen method, an offset method, a spray method, a dip method and the like are preferable.

It is preferable that the coating thickness of a porous insulating layer is 1-10 micrometers after drying, and 2-7 micrometers is more preferable. If the coating thickness is less than 1 μm after drying, the role of the porous insulating layer is insufficient to contribute to the improvement of safety. If the coating thickness is more than 10 μm, the safety may be improved, but the internal resistance of the battery may also increase to inhibit battery performance.

Hereinafter, a method of applying the porous insulating layer will be described in more detail.

First, the powder coating according to the first embodiment of the present invention will be described.

In order to apply the powder, an inorganic compound alone or an inorganic compound and a functional inorganic compound additive powder must be applied to the surface of the electrode layer before the applied electrode layer slurry is completely dried. At this time, when the mixed powder is applied, the inorganic compound and the functional additive are dry mixed in a sealed container in advance and then put into the coating step. In addition, the method of applying the powder may be applied in the same or partly modified if the powder coating method commonly used in the art, spray method and the like is preferable.

Hereinafter, application of the good solvent slurry according to the second embodiment of the present invention will be described.

In order to apply a good solvent slurry, an inorganic compound alone or a mixed powder of an inorganic compound and a functional inorganic compound additive is dissolved and dispersed in a solvent of the polymer binder. In the case of using a mixed powder, the inorganic compound and the functional additive are dry mixed in a sealed container in advance, and then put into the slurry mixing step. Slurry mixing is based on the same method as electrode layer slurry mixing.

After the polymer binder is completely dissolved and uniformly dispersed and mixed with the porous insulating layer constituent material, the slurry of the porous insulating layer should be applied to the surface of the electrode layer before the electrode layer slurry is completely dried. If it is a method which does not damage an electrode layer slurry, it is preferable, but a spray method is preferable.

Hereinafter, application of the non-solvent or poor solvent slurry according to the third embodiment of the present invention will be described.

In order to apply a non-solvent or poor solvent slurry, first, an inorganic compound alone or a mixed powder of an inorganic compound and a functional inorganic compound additive is dissolved and dispersed in a solvent of the polymer binder. In the case of using a mixed powder, the inorganic compound and the functional additive are dry mixed in a sealed container in advance, and then put into the slurry mixing step.

The slurry mixing may be performed in the same manner as the electrode layer slurry mixing method, but the difference from the second embodiment is that in the selection of the solvent and the polymer binder, the solvent of the polymer binder of the porous insulating layer coating slurry is applied to the polymer binder of the electrode layer slurry. It is a poor solvent or a nonsolvent.

After the polymer binder is completely dissolved and uniformly dispersed and mixed with the porous insulating layer constituent material, the porous insulating layer slurry is applied to the electrode layer surface before the electrode layer slurry is completely dried. Coating of the porous insulating layer is based on the same method as the electrode layer coating method, and any method that does not damage the electrode layer slurry, but spray method is preferred.

After transferring the electrode layer and the electrode coated with the porous insulating layer according to the first, second, and third embodiments to a drying furnace on the electrode current collector, the electrode layer and the porous insulating layer are completely dried to remove the solvent. Drying is applied according to the situation such as hot air method, direct heating method, induction heating method at a temperature such that each solvent is all volatilized.

The temperature is preferably 50 ℃ ~ 200 ℃, if it is below 50 ℃ may take a long time or incomplete to dry the solvent, if it is above 200 ℃ may damage the electrode constituent material and the electrode current collector. In addition, it is preferable to dry immediately after coating so that the porous insulating layer does not settle to the electrode layer due to the flow of the porous insulating layer and the slurry of the electrode layer, and before the porous insulating layer is applied, the electrode layer may be slightly dried to slightly reduce the flow of the electrode layer. have.

The secondary battery is manufactured by stacking the electrode in the completely dry state prepared by the above method in the order of a cathode-separator-anode together with a separator and then assembling it into a battery to absorb and package a liquid electrolyte. However, this is limited to the case where the porous insulating layer is coated on at least one surface of the positive electrode and the negative electrode.

2 is a schematic cross-sectional view of a secondary battery using an electrode according to an embodiment of the present invention. From the above process, a negative electrode coated with a porous insulating layer was placed below, and a separator and a positive electrode were laminated to constitute a battery. The negative electrode is electrically connected to the negative electrode current collector, and the positive electrode is electrically connected to the positive electrode current collector. The cathode porous insulating layer is coated on the surface of the cathode.

After the step of absorbing the liquid electrolyte in the assembly thus configured is a state capable of operating as a battery. In addition, a porous insulating layer may be applied to the surface of the anode, or a porous insulating layer may be applied to both the surface of the anode and the cathode.

[Example]

In the following, the method for producing an electrode, in particular a cathode according to the present invention will be described in detail. However, these examples do not limit the contents of the present invention, and modifications may be made without departing from the basic spirit of the present invention. For example, the same can be applied to the positive electrode, it is also possible to apply to both the positive electrode and the negative electrode.

Basic Example (Preparation of Undried Cathode)

N-methylpyrrolidone, a solvent of the binder, was added to the mixture consisting of 91 wt% graphite powder as the negative electrode material, 1 wt% carbon black as the conductive material, and 8 wt% polyvinylidene fluoride as the binder. While mixing to prepare a negative electrode mixture slurry having 50% solids. The negative electrode slurry was applied to a copper foil having a thickness of 10 μm, which is a negative electrode current collector, by a doctor blade method at a thickness of 150 μm to prepare an undried negative electrode.

Example 1 Powder Coating

Before the wet cathode obtained in the basic example was dried, silica having an average particle size of 100 nanometers was applied to the surface by a spray method in a powder state. The coating thickness was set to 3 μm after drying. In order to prevent the inorganic compound powder from settling into the electrode layer due to the flow of the slurry, the negative electrode was prepared by drying in a 120 ° C. hot air drying furnace for 5 minutes immediately after applying the roll press.

Example 2 (coating a good solvent slurry)

Before the wet cathode obtained in the basic example was dried, a separately mixed porous insulating layer slurry was applied to the surface by a spray method. The porous insulating layer slurry is an electrode compound polymer binder in a mixture consisting of 90 wt% of silica having an average particle size of 100 nanometers and 10 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) as an inorganic compound. N-methylpyrrolidone in a solvent relationship was added thereto and mixed for 4 hours in an oil stirrer to prepare a slurry having a solid content of 10%.

The coating thickness was set to 3 μm after drying, and dried in a hot air drying furnace at 120 ° C. for 5 minutes so that the porous insulating layer slurry or inorganic compound powder could not be settled and mixed into the electrode layer due to the flow of the slurry, and then the roll press was carried out. Prepared.

Example 3 (Poor Solvent / Non-solvent Slurry Application)

Before the wet cathode obtained in the basic example was dried, a separately mixed porous insulating layer slurry was applied to the surface by a spray method. The porous insulating layer slurry is an electrode compound polymer binder in a mixture consisting of 90 wt% of silica having an average particle size of 100 nanometers and 10 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) as an inorganic compound. Was added to the poor solvent acetone and mixed for 4 hours in an oil stirrer to prepare a slurry having a solid content of 10%.

The coating thickness was set to 3 μm after drying, and dried in a hot air drying furnace at 120 ° C. for 5 minutes so that the porous insulating layer slurry or inorganic compound powder could not be settled and mixed into the electrode layer due to the flow of the slurry, and then the roll press was carried out. Prepared.

[Comparative Example]

The undried negative electrode obtained in the basic example was dried in a 120 ° C. hot air drying furnace for 5 minutes to prepare a negative electrode coated only with an electrode layer.

Thereafter, a separately mixed porous insulating layer slurry was applied to the surface by a spray method. The porous insulating layer slurry is an electrode compound polymer binder in a mixture composed of 90 wt% of silica having an average particle size of 100 nanometers and 10 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) as an inorganic compound. Was added to the poor solvent acetone and mixed for 4 hours in an oil stirrer to prepare a slurry having a solid content of 10%.

The coating thickness was set to 3 μm after drying, followed by drying in a 120 ° C. hot air drying furnace for 5 minutes, and then performing a roll press to prepare a negative electrode.

The comparative example is different from Examples 1 to 3 in that the electrode layer slurry is applied, and after complete drying, the porous insulating layer slurry is applied again and dried to prepare a negative electrode. It is also possible to apply the porous insulating layer after the electrode layer is completely dried and roll pressed.

[Manufacturing Example]

Solvent of binder in a mixture consisting of 94 wt% lithium nickel cobalt manganese composite oxide (Li Ni1 / 3Co1 / 3Mn1 / 3 O2) as anode material, 3 wt% carbon black as conductive material, and 3 wt% polyvinylidene fluoride as binder Phosphorus N-methylpyrrolidone was added and mixed for 4 hours in the planetary stirrer in the same manner as the negative electrode of the comparative example to prepare a positive electrode mixture slurry having 50% solids. The positive electrode slurry was applied to an aluminum thin film having a thickness of 20 μm, which is a positive electrode current collector, by a doctor blade method at a thickness of 100 μm, dried for 5 minutes in a 120 ° C. hot air drying furnace, and rolled to prepare a positive electrode.

The negative electrode plate and the positive electrode plate, and the general separator for the secondary battery, cut each of the negative electrodes prepared from Examples 1 to 3 and Comparative Examples and the prepared examples to predetermined dimensions, were laminated and sequentially assembled in the order of negative electrode-separator-anode. . The laminate is placed in an aluminum pouch, which is an exterior material, and injected and sealed with a general electrolyte solution composed of an organic solution in which LiPF 6 lithium salt is dissolved at a concentration of 1.1 M in an EC and DEC (volume ratio 3: 7 composition) mixed organic solvent. Secondary batteries were prepared to be Preparation Example 1, Preparation Example 2, Preparation Example 3, and Comparative Preparation Example, respectively.

The main points according to Examples and Preparation Examples are summarized in Table 1 below.

Table 1 Electrode Composition and Preparation Example

[Experimental Example 1] <Capacity Maintenance Rate and Life Characteristics Experiments of Repeating Charge-Discharge of Secondary Battery>

The life characteristics of the secondary batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Examples were tested by the following conditions and methods, and the results are shown in a graph of FIG. 6.

In Experimental Example 1, the battery was charged at a constant current of 1.0C until the voltage rose to 4.2V, and then charged by applying a constant voltage of 4.2V until the current value dropped to 0.1C. Discharge was performed until

As shown in Figure 6, the secondary battery produced using the negative electrode of Examples 1 to 3 of the present invention (Preparation Examples 1 to 3) secondary (comparative manufacturing example) prepared using the prior art negative electrode of Comparative Example 1 When compared with a battery, it turns out that it expresses equal or more than the performance.

Experimental Example 2 <Capacity Expression According to the Discharge Current Application Value of the Secondary Battery>

The high rate discharge characteristics of the secondary batteries prepared in Preparation Example 1 and Comparative Preparation Example were tested by the following conditions and methods, and the results are shown graphically in FIG. 7.

In Experimental Example 2, the battery was charged at a constant current 1.0C until the voltage increased to 4.2V, and then charged with a constant voltage of 4.2V until the current value dropped to 0.1C. The constant current was 0.5C, 1.0C, 2C, and 5C, respectively. The discharge was performed until the voltage was lowered to 3.0 V at the speed of.

As shown in FIG. 7, the secondary battery manufactured by using the negative electrode of Example 1 (manufacturing example 1) compared to the secondary battery manufactured by using the prior art negative electrode of the comparative example (comparative example) had a performance equal to or greater than that of the secondary battery. It can be seen that the expression. This is because the porous structure of the negative electrode prepared in Example 1 was better formed than the negative electrode prepared in Comparative Example as described above, and thus, the electrolyte hygroscopicity and the ionic conductivity were improved.

Experimental Example 3 <Overcharge Safety Measurement Experiment>

The overcharge safety measurement experiments of the secondary batteries prepared in Preparation Examples 1 to 3 and Comparative Production Example were carried out according to the following conditions and methods, and the results are shown graphically in FIG. 8.

The battery voltage and the surface temperature of the battery were observed while the batteries prepared in Preparation Examples 1 to 3 and Comparative Preparation Example were overcharged to 12 V at a constant current of 32 A speed for 150 minutes.

In the case of Preparation Examples 1 to 3 and Comparative Preparation Examples, it can be seen from the graph of Figure 8 that both the internal short circuit did not occur and the battery maximum surface temperature is also very safe within 100 ℃. This is because thermal runaway is prevented by suppressing internal short circuit between the positive electrode and the negative electrode by the porous insulating layer applied to the negative electrode surface even if the internal temperature rises and thermal shrinkage deformation of the separator occurs. In the case of a secondary battery using an electrode having a porous insulating layer or an incomplete state, it is a general phenomenon that the battery ignites together with thermal runaway by causing a short circuit inside the battery due to a separator heat shrinkage deformation.

In Experimental Example 3, the battery was charged at a constant current 32A rate until the voltage increased to 12V, and then overcharged by applying a constant voltage of 12V for 150 minutes.

As shown in FIG. 8, when the secondary batteries manufactured using the negative electrodes of Examples 1 to 3 (Preparation Examples 1 to 3) were compared with the secondary batteries manufactured using the prior art negative electrodes of Comparative Examples (Comparative Preparation Example) It can be seen that the same level of safety. This means that the porous insulating layer according to the present invention exhibits the same function as the prior art.

As described above, the secondary battery electrode of the present invention coated with a porous insulating layer of the appropriate thickness through Experimental Example 1 to Experimental Example 3 does not impair battery performance, but rather is estimated to be improved electrode interface characteristics or electrolyte absorbency. For reasons, it was confirmed that the battery performance may be improved as compared with the prior art.

In addition, in various battery misuse situations such as overcharging, it was confirmed that the thermal contraction deformation of the separator may prevent an internal short circuit and an unsafe mechanism leading to thermal runaway.

5 is an SEM image of the negative electrode prepared in Example 1 of the present invention, the negative electrode prepared in Example 1 is a porous structure of the porous insulating layer is well formed, the negative electrode prepared in the comparative example shown in FIG. It can be confirmed that the porous structure of the electrode layer itself applied first is blocked by the binder constituting the porous insulation layer applied second.

10: umwinder 20: coater
30: dryer 40: rewinder
50: sprayer 100: electrode
110: positive electrode 120: positive electrode current collector
130: separator 150: porous insulating layer
160: negative electrode 170: negative electrode current collector

Claims (18)

In the electrode manufacturing method for forming a porous insulating layer on at least one electrode surface of the cathode or anode,
Applying an electrode layer slurry to the electrode surface;
Applying a porous insulating layer in an undried state of the electrode layer slurry;
Simultaneously drying the electrode layer slurry and the porous insulation layer coating slurry;
Secondary battery electrode manufacturing method comprising a porous insulating layer comprising a. The method of claim 1,
The porous insulating layer is a method of manufacturing an electrode for a secondary battery comprising a porous insulating layer is applied to the inorganic compound powder alone or applied by a mixed powder of the inorganic compound powder and functional inorganic compound additives. The method of claim 1,
The porous insulating layer is coated with a porous insulating layer coating slurry containing a polymer binder, the solvent of the polymer binder and the solvent of the polymer binder of the electrode layer slurry is volatile, a method for manufacturing an electrode for a secondary battery comprising a porous insulating layer is a good solvent. The method of claim 1,
The porous insulating layer is coated with a porous insulating layer coating slurry containing a polymer binder, the solvent of the polymer binder and the solvent of the polymer binder of the electrode layer slurry is a volatile, poor solvent or non-solvent electrode for a secondary battery comprising a porous insulating layer Way. The method of claim 1,
The electrode is a secondary battery electrode manufacturing method comprising a porous insulating layer containing an active material, a conductive material, a polymer binder, an additive. The method of claim 5,
If the electrode is a negative electrode, the active material is at least one of graphite or carbon-based material, and if the electrode is a positive electrode, the active material is transition metal-oxide, transition metal-phosphate, transition metal-silicate, transition metal- Method for producing a secondary battery electrode comprising a porous insulating layer, characterized in that at least one of sulfate or polymer material. The method of claim 5,
The conductive material is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that at least one selected from graphite, carbon black, activated carbon, carbon nanotubes, carbon nanofibers. The method of claim 5,
The polymer binder may be polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and maleic anhydride, polyvinyl chloride, polyvinyl alcohol, polyvinyl formal, poly Methyl methacrylate, polymethacrylate, tetraethylene glycol diacrylate, cellulose triacetate, polyurethane, polysulfone, polyether, polyolefin, polyethylene oxide, polyisobutylene, polybutyl diene, polyacrylonitrile, poly A method for producing an electrode for secondary batteries comprising a porous insulating layer, characterized in that at least one selected from mead, acrylonitrile-butadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene monomer, polydimethylsiloxane, and silicone polymer. The method according to any one of claims 3 to 4,
The solvent of the polymer binder is N-methylpyrrolidinone, dimethylformamide, dimethylacetamide, hexamethylphosphoamide, acetonitrile, acetone, cyclohexanone, dimethyl sulfoxide, tetrahydrofuran, dioxene, chloroform, dichloro At least one selected from methane and water, the electrode manufacturing method for a secondary battery comprising a porous insulating layer. The method of claim 4, wherein
The poor solvent or good solvent is at least selected from N-methylpyrrolidinone, water, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, glycerol, acetone, dimethyl ether, diethyl ether, ethyl acetate, dichloromethane A secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that one kind. The method of claim 2,
The inorganic compound powder includes a porous insulating layer, characterized in that at least one selected from SiO ₂ , Al ₂ O ₃ , TiO ₂ , SnO ₂ , ZnO, CeO ₂ , ZrO ₂ , BaTiO ₃ , Y ₂ O ₃ . Electrode manufacturing method for a secondary battery. The method of claim 11,
The inorganic compound powder is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that the size of 0.001 ~ 1 ㎛. The method of claim 11,
Content of the inorganic compound powder is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that at least 10% by weight of the porous insulating layer solids. The method of claim 2,
The additive of the functional inorganic compound is an electrode manufacturing method for a secondary battery comprising a porous insulating layer, characterized in that at least one selected from AlX ₃ , MgX ₂ , SnX ₂ .
Provided that X is a halogen element. The method of claim 14,
The additive of the functional inorganic compound is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that 0.1 to 10% by weight of the porous insulating layer solids. The method according to any one of claims 1 to 15.
Coating thickness of the porous insulating layer is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that 1 ~ 10㎛ after drying. The method according to any one of claims 1 to 15,
The porous insulating layer is a secondary battery electrode manufacturing method comprising a porous insulating layer, characterized in that the drying at 50 ℃ ~ 200 ℃. An electrode for forming a porous insulating layer on at least one electrode surface of a cathode or an anode,
An electrode layer slurry is coated on the surface of the electrode, and a porous insulating layer coating slurry is applied to the surface of the electrode layer slurry in an undried state of the electrode layer slurry to simultaneously dry the electrode layer slurry and the porous insulating layer coating slurry to bond the porous insulating layer. A secondary battery electrode comprising a porous insulating layer in which I do not block the porous structure of the electrode layer.

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